Method of testing a memory cell

ABSTRACT

As part of a memory array, a circuit is provided for altering the drive applied to an access transistor that regulates electrical communication within the memory array. In one embodiment, the circuit is used to alter the drive applied to a sense amp&#39;s voltage-pulling transistor, thereby allowing modification of the voltage-pulling rate for components of the sense amp. A sample of test data is written to the memory array and read several times at varying drive rates in order to determine the sense amp&#39;s ability to accommodate external circuitry. In another embodiment, the circuit is used to alter the drive applied to a bleeder device that regulates communication between the digit lines of the memory array and its cell plate. Slowing said communication allows defects within the memory array to have a more pronounced effect and hence increases the chances of finding such defects during testing. The circuit is configured to accept and apply a plurality of voltages, either through a contact pad or from a series of discrete voltage sources coupled to the circuit.

TECHNICAL FIELD

[0001] The present invention relates generally to semiconductor circuitdevices and, more specifically, to a circuit for changing the voltageapplied to selective portions of a memory array. Such portions includedigit line pairs as well as the gate of a transistor used to regulatesense amplifiers.

BACKGROUND OF THE INVENTION

[0002] In the operation of certain semiconductor circuit devices, pullupand pulldown sense amplifiers (sense amps) detect and amplify a smallcharge stored within a memory cell. In general, two complementary digitlines are attached to a pullup sense amp and a pull down sense amp. Atthe beginning of a reading operation, both lines are at an equilibratevoltage Veq, which is generally between the potential of a voltagesource used to operate the semiconductor device (V_(CC)) and groundpotential (0 volts). While Veq is changeable either intentionally orinadvertently through a defect, Veq is ideally equal to V_(CC)/2 duringnon-test operations. This midpoint voltage is defined as DVC₂.

[0003] One of the digit lines is coupled to a memory cell. The readingprocess involves a discharge from the memory cell to the correspondingdigit line, which creates a slight difference in voltage between the twodigit lines. This difference is then amplified by the sense amps: thedigit line with the slightly lower voltage has its voltage furtherdecreased by the pulldown sense amp, and the voltage of the other digitline is increased by the pullup sense amp. Once the voltage differencehas been amplified, the digit lines can then be used to operate lesssensitive circuitry.

[0004] Between reading cycles, it is necessary to return thecomplementary digit lines to Veq. This occurs during what is known as aprecharge cycle, wherein equilibration transistors short thecomplementary digit lines together. Further, a signal having a potentialof DVC₂ is communicated from a DVC₂ voltage generator to the shorteddigit lines through a bleeder device.

[0005] Concerning the operation of the sense amps, it should be notedthat pulling down the voltage of a digit line involves coupling the lineto ground through a pulldown transistor. Because an entire row of digitline pairs often connects to the same pulldown transistor through acommon node, the pulldown transistor will most likely have to drawcurrent from one line of each of several pairs. In doing so, there is arisk that the transistor will become saturated with current andtherefore become slower in pulling down the voltage of additional digitlines. This may lead to errors in reading, especially if an entire rowof memory cells is storing logic 1's except for one cell storing a logic0; for once the logic 0 is discharged, a slow pulldown may result in animproper reading of that logic 0 value.

[0006] One known way to solve this problem is to include an optionalactive area in the gate of the pulldown transistor. The increased sizeof the gate raises the threshold at which the pulldown transistorbecomes saturated. However, one of ordinary skill in the art willappreciate that this solution requires a costly metal mask change.Further, any attempt to speed up the slowed pulldown raises otherproblems in reading, as disclosed in U.S. Pat. No. 5,042,011, by Casper,et al. The Casper '011 reference discloses that pulling down the commonnode too quickly may result in capacitive coupling between the sourcesand drains of the sense amp's transistors. During capacitive coupling,both digit lines in one sense amp are pulled down before the common nodeis pulled down low enough to turn on one of the sense amp transistors.When the sense amp finally turns on, it shorts out the capacitivecoupling, bouncing the digit lines and, in the process, creates linenoise that will interfere with the ability to read the data properly.

[0007] Early saturation and capacitive coupling could be avoided if oneknew the margin— the difference in voltage between a logic 0 signal anda logic 1 signal—that the pulldown transistor was capable ofaccommodating. The only way to do so, as taught by the prior art, is toseparate the pulldown transistor with a laser and probe the gate.

[0008] As an alternative to determining the sense amp's margin, onecould simply test the sense amp's ability to operate at the given sourcevoltage used in non-test operations. Prior art suggests entering aseries of test data patterns into memory. Logic 1's are written to thecells of each memory array, with the exception of one column of logic0's. As a result, each row contains only one cell storing a logic 0,thereby creating the most likely circumstance for an error in readingthe data. The data in the array is then read and checked for errors.Once the first group of test data has been processed, a second sample oftest data is entered with the logic 0's written to the next column. Thisprocess repeats until a logic 0 has been written to and read from everycell in any given row in the memory array. The results will indicate thepulldown transistor's ability to read data accurately. The problem withthis process, however, is that it is time consuming to enter multiplesamples of test data.

[0009] Thus, there is a need in the art for a quicker circuit and methodfor testing the capabilities of a sense amp. Further benefit would bederived if this test could indicate the margin of the sense amp'spulldown transistor.

[0010] In addition to inadequate pulldown transistors, other problems,such as defects arising during the processing of semiconductor devices,may contribute to reading errors. Various techniques involvingequilibration of the complementary digit lines can be used duringtesting to detect these problems. For example, occasionally a digit linewill inadvertently have a short to ground. As a result, the potential ofthat digit line will leak towards 0 volts. To detect this problem, priorart teaches extending the time for the precharge cycle during a testmode. If the short has a low enough resistance, the short will overcomethe charging ability of the DVC₂ voltage generator, which remainscoupled to the digit lines, and Veq of the digit lines will decrease.Thus, a longer precharge cycle allows Veq to lower even further. As aresult, line noise is more likely to register as a logic 0 discharge onthe digit line when in fact the storage cell contains a logic 1 and hasnot yet discharged. Alternatively, assuming that a logic 1 is properlydischarged and sensed, a reading error is still likely: Veq may be solow due to the short that the pullup sense amp may not be able to pullup the digit line's voltage in time to register as a logic 1 forpurposes of driving external circuitry. Increasing the likelihood oferror is desirable in the test mode, as it helps to identify errors thatwould affect non-test operations. Further, a reading error occurringafter this extended precharge cycle will indicate the nature of thedefect—in this case a short in at least one of the digit lines. However,this testing process can be time consuming. As an example, a 64 meg DRAMhaving a 16 meg×4 configuration requires approximately 170 seconds tocarry out this test. It would be a benefit to the art to have a fasterway to test for this problem.

[0011] A second problem that could be detected by altering theequilibration rate of the digit lines involves a short between the cellplate and the digit line. The typical technique for discovering thisproblem is to initiate a long RAS (Row Address Strobe) low signal.During the low RAS, the digit lines are not equilibrated. Rather, theyare charged to their complementary voltage levels. Ideally, once the lowRAS ends and the lines are shorted, both digit lines should approach aVeq level of DVC₂. However, a short between one of the digit lines andthe cell plate will allow the DVC₂ generator 68 to change that digitline's voltage during the RAS low period. Thus, once the lines areshorted, their respective voltages will meet at a different Veq level.This will affect the margin between Veq and the voltage corresponding toone of the logic values and thereby increase the likelihood of a readingerror. Eventually, the signal from the DVC₂ voltage generator willrestore the proper equilibrate voltage once the RAS low signal ends.Nevertheless, for purposes of detecting this problem before non-testoperations begin, it would be desirable to slow the restoration of theproper Veq level.

[0012] A third example concerns a defect that could exist within thememory cell's storage capacitor, such as a defect in a nitride layeracting as a dielectric between the memory cell's conductive plates. Sucha defect could cause a short within the storage capacitor. Because thestorage capacitors are coupled to the DVC₂ voltage generator, adefective capacitor “storing” a 0 volt charge, representing a logic 0,will slowly charge to the DVC₂ level. The closer the storage capacitorapproaches a DVC₂ charge, the more likely that a logic 1 value may bemisread during the next reading. One way to detect this problem in theprior art is to initiate a static refresh pause, wherein the memorycell's access transistor remains deactivated for a longer time thanusual—generally 100 milliseconds. As a result, the capacitor, whichshould be storing a logic 0, has a longer time to charge to a highervoltage, thereby making an error in the next reading cycle more likely.

[0013] Once again, a speedier test is desired. The defect might bedetected earlier if the problem were exacerbated to the point where theleaked charge for the stored logic 0 exceeded the equilibrate charge ofthe digit lines. As a result, a logic 1 would be read from the cell eventhough it was known that a logic 0 had been written. One could speed upthe leakage into the storage capacitor by forcing DVC₂ to a highervoltage. However, the equilibrate voltage of the digit lines would alsoincrease accordingly and remain higher than the voltage of the charge inthe storage capacitor. Thus, forcing DVC₂ would not appreciably increasethe ability to detect an error unless the equilibration of the digitlines could be slowed. The only way to do this in the prior art isthrough the use of a costly metal option to change the gate voltage ofthe bleeder device.

SUMMARY OF THE INVENTION

[0014] Given the need for regulating the drive of a sense amp, as wellas the need for regulating the equilibration signal from a DVC₂ voltagegenerator, a test circuit is provided for varying the voltage of asignal used to drive a connection device that allows electricalcommunication within a semiconductor circuit. One preferred circuitembodiment includes a contact pad for carrying a range of test voltagesignals to said connection device. In another preferred circuitembodiment, a regulator circuit enables a series of discrete voltages todrive the connection device.

[0015] In one set of applications involving the regulation of a senseamp, the connection device comprises a sense amp's voltage pullingtransistor. Any circuit embodiment covered by the present invention canbe used to test drive the transistor. In a preferred method of use, atest data pattern is entered and the data is read several times, with adifferent voltage driving the sense amp's pulldown transistor each time.One advantage of this preferred method is that it reduces the need forentering several elaborate test data patterns and, therefore, allows forquicker testing of memory arrays. A second advantage is that theembodied method and devices allow a determination of the lowest supplyvoltage that can be used during normal operation without errors inreading data. Yet another advantage is the ability to determine thehighest supply voltage, and therefore the fastest reading speed, thatcan be used during normal operations without causing capacitivecoupling. In doing so, the preferred circuit embodiments and methodincrease the sense amp's ability to distinguish between a logic 0voltage and a logic 1 voltage without physically altering the sense amp.Further, in the process of determining the lowest and highest voltagesat which the sense amp is capable of functioning, the preferredembodiments and method also provide a way to ascertain the marginwithout dissecting components of the sense amp.

[0016] Concerning the specific errors that may be detected in relationto equilibrating the digit lines, the connection device comprises anisolation bleeder device coupled between the DVC₂ voltage generator anda digit line pair. The circuit embodiments provide a test mode apparatusfor driving the bleeder device in order to slow or quicken theequilibration of the digit line pair. Applying these embodimentsprovides the advantage of a quicker detection of defects such as a shortfrom a digit line to ground, a short from a digit line to a cell plate,and a short within the storage capacitor of a memory cell. Theembodiments also provide an alternative advantage of overcoming theinfluence of these defects during non-test modes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 depicts a row of n-channel pulldown sense amps withassociated D, D*, and WL lines; a pullup sense amp; and a series ofmemory cells, as found in the prior art. FIG. 1 also shows a digit lineequilibration circuit as found in the prior art.

[0018]FIG. 2 is a graph indicating the voltage of the conductive paths Dand D* over time in the event that a memory cell storing a logic 0discharges to D. FIG. 2 also demonstrates the resulting amplification ofthe difference in voltage.

[0019]FIG. 3 is a graph demonstrating the relationship between drivecurrent (I_(DV)) and the gate-source voltage of a pulldown transistor(V_(GS)) at various levels of voltage applied to the gate (V_(GATE)).

[0020]FIG. 4 details one exemplary circuit embodiment in accordance withthe present invention as used with a sense amp.

[0021]FIG. 5 illustrates a second exemplary circuit embodiment inaccordance with the present invention as used with a sense amp.

[0022]FIG. 6 shows a third exemplary circuit embodiment in accordancewith the present invention as used with a sense amp.

[0023]FIG. 7a is a schematic of a portion of a memory array depicting anembodiment of the current invention as used in the digit line/cell plateregion of a memory array. FIG. 7a further depicts a first type ofpossible defect within said memory array.

[0024]FIG. 7b is a graph illustrating the effect of the first defect anda first embodied method of the current invention.

[0025]FIG. 7c is another graph illustrating the effect of the firstdefect and the first embodied method of the current invention.

[0026]FIG. 8a depicts a cross-section of a portion of a memory arrayincluding a second type of defect.

[0027]FIG. 8b demonstrates the effect on a memory array of the secondtype of defect as well as the effect of a second embodied method of thecurrent invention.

[0028]FIG. 8c further demonstrates the effect on a memory array of thesecond type of defect as well as the effect of a third embodied methodof the current invention.

[0029]FIG. 8d depicts the effect of a fourth embodied method of thecurrent invention as it relates to the second type of defect.

[0030]FIG. 9a is a schematic of a portion of a memory array depicting athird type of defect in said memory array.

[0031]FIG. 9b is a graph indicating the effect of the third type ofdefect.

[0032]FIG. 9c is a graph illustrating a method in the prior art fordetecting the third type of defect.

[0033]FIG. 9d is a graph illustrating the effect of a fifth embodiedmethod of the current invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034]FIG. 1 illustrates the general configuration of sense amps in amemory array. A pulldown sense amp 20 includes cross coupled n-channeltransistors Q1 and Q2, as well as a pulldown transistor Q3, which is ann-channel transistor driven by a signal designated as LENSA. Theseelements play a part in sensing and amplifying a voltage differencebetween D and D* caused by shorting a memory cell 22 to D by way ofaccess transistor Q4. The sources of Q1 and Q2 are connected to a commonpulldown node 24, and the gate of each is connected to the other'sdrain. The gate of Q1 also connects to the line D*, whereas the gate ofQ2 connects to the line D.

[0035] As discussed above, each line D and its corresponding line D* areinitially at the same voltage DVC₂. For purposes of explanation, DVC₂ isassumed to be 1.65 volts, or one half of the source voltage V_(CC),which is 3.3 volts. Lines D and D* connect to opposite sides of eachsense amp 20. Common pulldown nodes 24 found in the sense amp arrayswill also be at DVC₂. A signal sent through the path WL will cause astorage capacitor 150 of particular memory cell 22 to discharge to aline D, thereby slightly changing D's voltage while the voltage of D*remains at DVC₂. Again, for purposes of explanation, a memory celldischarge will be assumed to cause a 0.2 volt difference in D. Thepulldown sense amp 20 will then turn on when the common pulldown node 24is one transistor threshold voltage below D or D*, whichever is highest.For instance, if a memory cell 22 is storing a logic 1, a discharge to Dwill increase D's voltage to 1.85 volts. As a result, the pulldown senseamp transistor gated by D (Q2) turns on faster than the one gated by D*(Q1). With transistor Q2 on, D*'s voltage is pulled down from 1.65 voltstowards ground as the common pulldown node 24 is pulled down as well.Further, the lowering voltage of D* serves to turn on the pullup senseamp transistor gated by D* (Q14) before the other pullup sense amptransistor turns on. The voltage supply V_(CC) then charges line D.

[0036] On the other hand, if the memory cell 22 had been storing a logic0, then a discharge to D would slightly lower D's voltage to 1.45 volts.The pulldown sense amp transistor gated by D* (Q1) would turn on firstand D's voltage would be further decreased toward ground by the pulldownsense amp, thereby allowing the pullup sense amp to increase D*'svoltage toward V_(CC). In this way, a small voltage difference between Dand D* is sensed and amplified. Once the voltage difference has beenamplified, D and D* can drive less sensitive circuitry not shown inFIG. 1. It should be noted that, if a logic 0 is transmitted to D, thenthe pulldown sense amp need only pull down D from 1.45 volts. If a logic1 is transmitted to D, then the pulldown sense amp must pull D* from thehigher DVC₂ level—1.65 volts.

[0037] Therefore, if many logic 1's in a memory array row are read, theextra voltage that must be pulled contributes to saturating the pulldowntransistor Q3 with drive current, thereby slowing any further pulldown.The problem created by slow pulldown is illustrated in FIG. 2, whereslope X denotes the initial discharge to D from a memory cell 22 storinga logic 0. FIG. 2 further illustrates the amplification of thedifference in voltage between D and D*. Slope Y denotes the timerequired for D to drop in voltage given a situation where a row of cellscontains a roughly equal number of logic 1's and logic 0's. Should therebe many logic 1's read amongst a single logic 0, then the outcomechanges: as the logic 0 is read, the pulldown transistor Q3, havingapproached saturation, takes much longer to pull down D's voltage. Thisresult is illustrated by slope Z. Other circuitry elements (not shown)that are driven by D may read D before its transition to a lower voltagehas been completed. As a result, a logic 0 value may be misread as alogic 1.

[0038] As illustrated in FIG. 3, increasing the voltage to the gate ofthe pulldown transistor allows the transistor to pulldown more currentbefore saturation. One preferred embodiment of the current inventionthat uses this principal is detailed in FIG. 4, where the pulldowntransistor Q3 is driven by a test circuit 26 through an inverter 27. Inthis embodiment, the inverter 27 comprises a p-channel transistor Q6 andan n-channel transistor Q8. The coupled gates of inverter transistors Q6and Q8 form an input node 28 for receiving a signal ENSA*, which may beV_(CC), ground, or a signal from another driver. The coupled drains ofthe inverter transistors Q6 and Q8 output the LENSA signal that drivesthe pulldown transistor Q3. The source of Q8 is coupled to ground. Thesource of Q6 is coupled to a source node 30 that branches into a firstconducting path 32 and a second conducting path 34. The first conductingpath 32 is coupled to an n-channel transistor Q10, which has a channelwidth-to-length ratio of around 500/2. The drain of transistor Q10 iscoupled to a contact pad 36. It should be understood that the term“contact pad” includes any conductive surface configured to permitelectrical communication with a circuit or a node. The gate oftransistor Q10 is coupled to an inverter 60 through another n-channeltransistor Q36. Together, inverter 60 and transistor Q36 comprise alatch device, and both are coupled to V_(CCP). Further, inverter 60receives a TEST* signal as an input. In addition, the gate of transistorQ10 is also coupled to a feedback capacitor 62. This feedback capacitor62 comprises an n-channel transistor having a size of approximately100/100, wherein the drain and source are shorted and coupled to thefirst conductive path 32. The second conducting path 34 is coupled to ap-channel transistor Q12, driven by a signal TEST, which is understoodto be the complement of TEST*. The transistor Q12 is also coupled toV_(CC), although no voltage source is considered to be a part of theinvention.

[0039] During testing, TEST* transmits a low voltage signal which isreceived by the inverter 60. In response, the inverter 60 initiates aV_(CCP) signal, sending it through transistor Q36 which outputs theV_(CCP) signal to the gate of transistor Q10, thereby switching on Q10.The feedback capacitor 62 serves to maintain and replenish this V_(CCP)signal in the event of leakage. Capacitive coupling between the gate anddrain of transistor Q10 allows Q10 to carry signals having a range ofvoltages for modifying the drive of the pulldown transistor Q3.Simultaneously, the TEST signal, applying a high voltage to transistorQ12, isolates V_(CC). A test data pattern is entered into the memorycells 22 and read with varying voltages driving the pulldown transistorQ3. The data read at various alternate voltages sent through bond pad 36can be compared with the data as originally written. This series ofreadings indicates the range of voltages through which the pulldowntransistor Q3 is capable of allowing accurate data readings. Oncetesting has ended, TEST* sends a high voltage signal and TEST becomeslow, thereby isolating the bond pad and allowing the V_(CC) signal totransmit to the pulldown transistor Q3.

[0040] The embodiment illustrated in FIG. 5 is a package part of thesemiconductor circuit device and receives a plurality of voltage sourceswith different magnitudes. The test circuit 26 allows selection amongthese sources for driving the gate of the pulldown transistor Q3. Theinverter 27 is the same as in FIG. 4. In this exemplary embodiment,however, source node 30 is coupled to three discrete voltage sources.First, source node 30 is coupled to V_(CCP) through a p-channeltransistor Q20 that is driven by a low signal A*. Source node 30 is alsocoupled to DVC₂ through another p-channel transistor Q22 that is drivenby a low signal B*. Finally, source node 30 is coupled to V_(CC) by wayof a p-channel transistor Q24. This p-channel transistor Q24 is gated bythe output of a logic unit, such as a NAND gate 46, which will drivetransistor Q24 in response to receiving a high signal A as a first inputand a high signal B as a second input. Given the input vector scheme ofthis embodiment, one of the transistors Q20, Q22, or Q24 will beoperable to the exclusion of the other two.

[0041] Thus, a low signal A* will drive the p-channel transistor Q20,thereby allowing V_(CCP) to drive the pulldown transistor Q3.Simultaneously, signal B will be high, turning off p-channel transistorQ22. Further, the NAND gate output will also be high and turn offp-channel transistor Q24. If, on the other hand, signal B is low andsignal A is high, then only p-channel transistor Q22 will be on,allowing DVC₂ to transmit to the pulldown transistor Q3. Only when bothsignals A and B are high does the NAND gate 46 output a low signal andallow V_(CC) drive the pulldown transistor Q3. The data read at thesethree voltage levels can then be compared with the data as originallywritten. It should be noted that this configuration does not require thedie space needed for the contact pad 36.

[0042] Another embodiment concerns varying the voltage applied to apullup sense amp 40. As seen in FIG. 1, the pullup sense amp 40 includescross coupled p-channel transistors Q14 and Q16 as well as a pulluptransistor Q18. As one of ordinary skill in the art understands, thereis generally a pullup sense amp 40 corresponding to every pulldown senseamp. Nevertheless, for purposes of clarity, only one pullup sense amp 40is shown. The sources of Q14 and Q16 are connected to a common pullupnode 42, and the gate of each is connected to the other's drain.Further, the gate of Q14 connects to line D*, and the gate of Q16connects to line D. Common pullup node 42 is coupled with pulluptransistor Q18, which is another p-channel transistor. Pullup transistorQ18 is also coupled to the voltage source V_(CC). The pullup transistorQ18 is driven by a signal LEPSA*. FIG. 6 illustrates that the voltagedriving pullup transistor Q18 may also be varied through the use of atest circuit 26 analogous to that used with the pulldown transistor Q3in FIG. 5. FIG. 6 depicts an inverter 27 comprising a p-channeltransistor Q26 and an n-channel transistor Q28. The coupled gates ofinverter transistors Q26 and Q28 form an input pathway 48 for a controlsignal designated EPSA. The coupled drains transmit the inverted outputsignal EPSA* which, in turn, is received by a prior art device 50 thatoutputs the LEPSA* signal used to drive the pullup transistor Q18. Thesource of Q26 is coupled to V_(CC), whereas the source of Q28 is coupledto the test circuit 26 which, in this embodiment, includes threeconductive paths. The first path 52 leads to DVC₂ by way of an n-channeltransistor Q30, which is driven by a signal C. The second path 54 iscoupled to a voltage source V_(BB) through an n-channel transistor Q32,as driven by a signal D. The third path 56 leads to ground by way ofn-channel transistor Q34. The gate of n-channel transistor Q34 iscoupled to the output of a NOR gate 58. The NOR gate 58 accepts signal Cas a first input and signal D as a second input and will activatetransistor Q34 only when both signals are low. Further, this embodimentis configured in a manner analogous to the embodiment in FIG. 5, in thatsignals C and D will never simultaneously activate their respectivetransistors Q30 and Q32.

[0043] The three n-channel transistors Q30, Q32, and Q34 will turn on ifa high, or logic 1, signal is transmitted to their respective gates. Aswith the embodiment shown in FIG. 5 for the pulldown sense amp, thesignals and transistors are configured to allow only selectivecommunication between one voltage source and the pullup transistor Q18.As a result, if signal C is high, it will latch the n-channel transistorQ30 and provide electrical communication between DVC₂ and the pulluptransistor Q18. At the same time, the low signal from D turns offn-channel transistor Q32. Under these circumstances, the signals C and Dalso result in a low signal output from the NOR gate 58, thereby turningoff n-channel transistor Q34. Thus, all of the other voltage sources areisolated. Similarly, if signal D is high, then only n-channel transistorQ32 is turned on and V_(BB) electrically communicates with pulluptransistor Q18. When both signals are low, the NOR gate 58 outputs ahigh signal, thereby grounding the source of the n-channel invertertransistor Q28. This embodiment has benefits similar to the embodimentin FIG. 5.

[0044] Returning to FIG. 1, a prior art equilibration circuit can beseen as part of the memory device. For purposes of explaining thefollowing embodiments of this invention, V_(CC) is now presumed to be 5volts. A transistor Q101 is coupled between digit line D and itscomplementary digit line D*. The transistor is driven by anequilibration signal EQ. It should be noted that the signal EQ resultsfrom a logic function and is distinguishable from the equilibratevoltage Veq, which represents the common mid-range voltage level of thecomplementary digit lines before a reading operation.

[0045] The signal EQ also drives two additional transistors Q102 andQ103, which are connected together in series at a node 120. Theseconnected transistors Q102 and Q103 are also coupled between lines D andD*. Moreover, node 120 is coupled to a cell plate 138 and a DVC₂ voltagegenerator 68 through a bleeder device 122. The DVC₂ voltage generator 68transmits a cell plate signal CP of voltage DVC₂ to the node 120. Forpurposes of explaining the following embodiments of this invention, DVC₂is now 2.5 volts. The bleeder device 122 is driven by a signal ofvoltage V_(CCP), wherein V_(CCP) results from having pumped V_(CC) to aneven higher potential.

[0046] At the beginning of a precharge cycle, digit line D and itscomplementary digit line D* are at different voltages as a result of adischarge of the memory cell 22 during the reading cycle. One line willhave a charge equal to the V_(CC) value of 5 volts, while the other linewill have a 0 volt charge. The equilibrate signal EQ is then sent,activating transistor Q101, which shorts D and D* together. Moreover,the signal EQ activates transistors Q102 and Q103, which not onlyprovide another short between D and D* but also allow the CP signal tobe communicated to those lines. As a result, the lines D and D*equilibrate, both gaining a charge of potential DVC₂ (2.5 volts), whichis the desired equilibrate voltage Veq in this example. Once the linesare equilibrated, they are ready for further testing.

[0047] For various reasons, a particular portion of the memory array maybe defective. Hopefully, testing processes will identify those defects.As discussed above and illustrated in FIG. 7a, a first defect 124 thatmay exist as a short to ground of the digit line D. FIG. 7b illustratesthe effect of the first defect 124. During the precharge cycle, the CPsignal is trying to charge the digit lines D and D* to the 2.5 volt DVC₂level and maintain that level. However, if the resistance of the shortis not too great, the first defect 124 may cause the digit lines todischarge toward ground faster than CP can charge them to 2.5 volts. Asa result, once the precharge process has ended at time t₁, the digitlines may be equilibrated at a potential lower than 2.5 volts, such as1.7 volts. Having a Veq at a level other than DVC₂ makes the memoryarray susceptible to reading errors. For example, in the presentsituation illustrated in FIG. 7b, where Veq is too low, line noise on Doccurring at time t₂ is more likely to register as a logic 0 dischargewhen in fact the storage cell 150 contains a logic 1 and has not yetdischarged. Alternatively, assuming that a logic 1 is properlydischarged and sensed at time t₂′, a reading error is still likely: asseen in FIG. 7c, Veq may be so low due to the short that the pullupsense amp may not be able to sufficiently pull up the digit line'svoltage by the time t₃, when external circuitry accesses line D. Inorder to find such a reading error, prior art requires an extendedprecharge time, up to time t₁, in order to allow the discharge from thefirst defect 124 to overtake the charge from CP.

[0048] The current invention, however, provides an alternative torequiring a long precharge time. FIG. 7a illustrates that the V_(CCP)signal driving the bleeder device has been replaced with the testcircuit 26 that applies a different voltage V_(REG) to regulate thebleeder device. In the case of the first defect 124, the test circuit 26transmits a signal having a voltage lower than V_(CCP) to drive thebleeder device 122. This causes a slower charge rate and allows thedischarge from the first defect 124 to quickly overtake the chargingfrom CP, as seen by the dashed lines in FIGS. 7b and 7 c. With theresulting increased disparity between the charge rate and the dischargerate, the precharge period need only endure until time t₁′ in order toincrease the likelihood of detecting an error.

[0049] The design of test circuit 26 can be the same as those used inFIGS. 4 and 5, wherein a source node 30 has access to at least one testvoltage, either through a bond pad 36 or from a discrete voltage source.In this application, however, the source node 30 is coupled to thebleeder device 122. Furthermore, V_(CCP) is the voltage used in non-testoperations to drive the bleeder device, and V_(CC) and DVC₂ are used toslow the charge rate. It should be further understood that the number ofvoltage options could be increased. Alternatively, the number of voltageoptions could be decreased to offer only one test voltage and onenon-test voltage.

[0050] These circuit embodiments, as well as others falling under thescope of the invention, have uses in detecting other defects. FIG. 8aillustrates another defect 136 that might occur within a memory array.The cross-sectional view in FIG. 8a shows the cell plate 138 coupled toa first n-region 140 of access transistor Q4. Ideally, the only way forthe DVC₂ voltage generator 68 to charge the digit line D through thecell plate 138 is to drive the gate 142 of transistor Q4 so that thecharge may pass from the first n-region 140 to a second n-region 144.From there, the charge travels through a tungsten plug 146, which servesas a contact between the second n-region 144 and the digit line D.Occasionally, however, a second defect 136 in the memory array may occurin the form of a short between the cell plate 138 and the tungsten plug146. As discussed above, a long RAS low signal is used to detect thissecond defect 136. Assuming line D is charged to 0 volts, FIG. 8b showsthat the long RAS signal allows line D to be charged to a highervoltage. Thus, when the low RAS signal ends at time t₁ and the digitlines are shorted to begin equilibration, the digit lines will no longerhave an initial tendency to reach an average potential between 5 and 0volts (2.5 volts). Rather, because line D is now higher than 0 volts,the shorted lines will settle at a higher midpoint, such as 3.5 volts.At this point, the margin between the new equilibrate voltage and thevoltage representing a logic 1 has decreased. Thus, an erroneous readingis more likely, as discussed above.

[0051] Conversely, if line D is initially charged to V_(CC) (FIG. 8c),the short to the cell plate will cause D's voltage to lower during along RAS low period. The resulting equilibrate voltage of lines D and D*could be lower than the preferred 2.5 volts. The lower equilibrate wouldagain make an error in reading more likely. In either case, the CPsignal will restore the equilibrate voltage to 2.5 volts by time t₂.However, by decreasing the drive to the bleeder device 122, any of theembodiments of the current invention will serve to slow down therestoration of Veq to DVC₂. With restoration time extended to time t₂′,any circuit embodiment of the current invention increases the likelihoodof detecting errors that would suggest the existence of the seconddefect 136. Alternatively, FIG. 8d shows that a circuit embodiment ofthe current invention could be used during a non-test mode to compensatefor the second defect 136 by driving the isolation device 122 at ahigher-than-normal level. As discussed above, the bleeder device 122 isnormally driven at V_(CCP), a voltage level representing one or twoV_(t)'s above V_(CC). The potential V_(t), in turn, is the thresholdvoltage of the bleeder device 122. A further increase in the potentialof V_(CCP) would allow the bleeder device 122 to quickly restore Veq to2.5 volts by time t₂″. The shorter restoration period reduces thechances of an erroneous reading.

[0052]FIG. 9a demonstrates yet another instance wherein the currentinvention could shorten test time. This instance concerns a third defect148 comprising a short that may be caused by a nitride defect within thestorage capacitor 150 of a memory cell 22. It should also be noted thatone of the plates of the storage capacitor 150 is in fact the cell plate138 and is therefore connected to the DVC₂ generator. Given this thirddefect 148, FIG. 9b indicates that the CP signal, having a potential ofDVC₂, will charge the storage capacitor 150 toward that potential eventhough a logic 0 has been written to that cell for test purposes. Duringa static refresh pause, the word line WL leading to the memory cell 22will continuously transmit a low signal, which turns off accesstransistor Q4 of the memory cell 22 and allows the storage capacitor 150to take on a greater charge. With the stored charge having a highervoltage, such as 2 volts, it is more likely that the logic 0 will bemisread at line D as a logic 1. In order to speed up the leakage intothe storage capacitor 150, DVC₂ is forced to a voltage higher than thenormal 2.5 volts. Unfortunately, this would not result in much benefitunder the prior art, as demonstrated by FIG. 9c: because the CP signalhas a voltage of DVC₂ and is in communication with D and D* during thestatic refresh pause, the CP signal would also charge lines D and D* toa higher voltage. With the circuit embodiments of the present invention,however, a lower voltage could be used to drive the bleeder device 122and thereby slow the charging of the digit lines, as illustrated in FIG.9d. Thus, while D and D* are regulated to substantially remain at 2.5volts despite the forced DVC₂ voltage, the storage capacitor may bequickly charged to a higher potential, such as 2.7 volts, which exceedsthe equilibrate voltage and makes it very likely that a logic 1 will bemistakenly recognized.

[0053] One of ordinary skill can appreciate that, although specificembodiments of this invention have been described for purposes ofillustration, various modifications can be made without departing fromthe spirit and scope of the invention. Concerning the invention as usedwith a sense amp, for example, a test circuit for the pullup sense ampcould be configured to transmit an entire range of voltages through acontact pad, as done with the pulldown sense amp depicted in FIG. 4. Inaddition, the test circuit 26 in FIG. 6 could be used with a pulldownsense amp. Conversely, the test circuit 26 in FIG. 5 could be used witha pullup sense amp. Moreover, both of these test circuits could becoupled to the same inverter and used to test drive either type of senseamp.

[0054] Further, regarding the embodiments use with a cell plate, itshould be noted that the embodiments may be applied for other testing.Any circuit embodiment, for instance, may be used during the prechargecycle discussed above in order to detect a short between a row line anda column line. Moreover, a circuit embodiment of the current inventioncould also be used during a non-test mode to overcome other defects inaddition to the short between a digit line and cell plate, as describedabove.

[0055] It should also be noted that, given a particular voltage sourceused in an embodiment, that source can be independent of V_(CC) ratherthan a mere alteration of V_(CC), such as V_(CCP) or DVC₂. Accordingly,the invention is not limited except as stated in the claims.

What is claimed is:
 1. A test mode drive-modifying device for a memoryarray having at least one sense amp coupled to a voltage-pullingmechanism, comprising: a test voltage alteration mechanism, wherein:said test voltage alteration mechanism is coupled to saidvoltage-pulling mechanism; and said test voltage alteration mechanism isconfigured to receive a plurality of voltages.
 2. The test modedrive-modifying device in claim 1 , wherein said sense amp is a pulldownsense amp.
 3. The test mode drive-modifying device in claim 2 , whereinsaid voltage-pulling mechanism is a transistor.
 4. The test modedrive-modifying device in claim 3 , wherein said voltage-pullingmechanism is an n-channel transistor.
 5. A test mode driver circuit fora voltage-pulling transistor of a sense amp, comprising: a conductivepath coupled to a gate of said voltage-pulling transistor; and anapparatus configured to receive a range of voltages coupled to saidconductive path.
 6. The test mode driver circuit in claim 5 , whereinsaid apparatus is a contact pad.
 7. A voltage-pulling circuit for asense amp, comprising: a main conductive path coupled to said sense amp;and a plurality of secondary conductive paths selectively coupled tosaid main conductive path, wherein each of said plurality of secondaryconductive paths is configured to receive a generally discrete voltage.8. The voltage-pulling circuit in claim 7 , wherein said sense amp is apullup sense amp.
 9. A driving circuit for a voltage-pulling transistorof a sense amp, comprising: a selective coupling apparatus coupled toand electrically interposed between: a test conduit configured to accepta plurality of voltage signals; and an output node configured to coupleto a gate of said voltage-pulling transistor; wherein said selectivecoupling apparatus has a first mode of operation and is configured toreceive a signal that has a first value during said first mode ofoperation, and wherein said selective coupling apparatus is furtherconfigured to allow electrical communication between said test conduitand said output node in response to said first value.
 10. The circuit inclaim 9 , further comprising a main conduit coupled to said selectivecoupling apparatus and configured to receive a voltage source, andwherein: said selective coupling apparatus has a second mode ofoperation; said signal has a second value during said second mode ofoperation; and said selective coupling apparatus is configured to allowelectrical communication between said main conduit and said output nodein response to said second value.
 11. The circuit in claim 10 , whereinsaid selective coupling apparatus is configured to prevent electricalcommunication between said test conduit and said output node in responseto said second value.
 12. The circuit in claim 11 , wherein saidselective coupling apparatus is configured to prevent electricalcommunication between said main conduit and said output node in responseto said first value.
 13. The circuit in claim 12 , wherein said secondvalue is inverse to said first value.
 14. A voltage regulator for avoltage-pulling transistor of a sense amp, wherein said voltage-pullingtransistor is driven by an inverter circuit having a p-channeltransistor and an n-channel transistor, comprising: a common nodeconfigured to couple to said inverter circuit; a first electricalconnection device electrically interposed between said common node and afirst pathway, wherein: said first pathway is configured to accept afirst voltage, and said first electrical connection device is configuredto accept a first vector and to electrically connect said first pathwaywith said common node in response to said first vector; and a secondelectrical connection device electrically interposed between said commonnode and a second pathway, wherein: said second pathway is configured toaccept a second voltage, and said second electrical connection device isconfigured to accept a second vector and electrically connect saidsecond pathway with said common node in response to said second vector.15. The voltage regulator in claim 14 , wherein said voltage regulatoris configured to accept one of said first and second vectors at a time.16. The voltage regulator of claim 15 , wherein said voltage regulatoris a package part of an integrated circuit.
 17. The voltage regulator inclaim 16 , wherein said common node is coupled to said p-channeltransistor.
 18. The voltage regulator of claim 15 , further comprising alatch device connected to said second electrical connection device,wherein: said latch device is configured to receive a test vector; andsaid latch device is further configured to transmit said second vectorto said second electrical connection device in response to said testvector.
 19. The voltage regulator of claim 18 , wherein said latchdevice further comprises: an inverter connected to said secondelectrical connection device, wherein: said inverter is configured toreceive said test vector, and said inverter is further configured totransmit said second vector to said second electrical connection devicein response to said test vector; and an activated transistorelectrically interposed between said second electrical connection deviceand said inverter.
 20. The voltage regulator of claim 19 , furthercomprising a replenish device coupled to said second electricalconnection device and to said common node, wherein said replenish deviceis configured to substantially maintain a potential at said secondelectrical connection device.
 21. The voltage regulator of claim 20 ,wherein said replenish device is a capacitor;
 22. The voltage regulatorof claim 21 , wherein: said replenish device comprises a secondn-channel transistor having a gate, a drain and a source; said drain andsaid source are coupled together at a capacitance node; said capacitancenode is coupled to said common node; and said gate is coupled to saidsecond electrical connection device.
 23. A margin-range apparatus for asense amp's voltage-pulling transistor driven by an inverter circuithaving a p-channel transistor coupled to an n-channel transistor,comprising: a voltage reception device, wherein: said voltage receptiondevice is configured to couple to said inverter circuit, and saidvoltage reception device is selectively coupled to a first test voltagepath and a second test voltage path.
 24. The apparatus in claim 23 ,wherein said voltage reception device is selectively coupled to a groundpath.
 25. The apparatus in claim 24 , wherein said voltage receptiondevice is coupled to said n-channel transistor.
 26. A current saturationtest device for a sense amp having a pullup transistor gated by aninverter comprising a p-channel transistor and an n-channel transistor,wherein said device comprises: a first terminal configured to couple tosaid inverter and adapted to receive a generally constant potential; anda second terminal configured to couple to said inverter and adapted toreceive a plurality of voltage potentials.
 27. The device in claim 26 ,wherein said second terminal is coupled to: a first test path adapted toreceive a first test voltage; a second test path adapted to receive asecond test voltage; and a non-test path coupled to a potential node.28. The device in claim 27 , further comprising: a first selectiondevice coupled to said first test path and electrically interposedbetween said second terminal and said first test voltage, wherein saidfirst selection device is configured to activate in response to a firsttest signal; a second selection device coupled to said second test pathand electrically interposed between said second terminal and said secondtest voltage, wherein said second selection device is configured toactivate in response to a second test signal; and a third selectiondevice coupled to said non-test path, electrically interposed betweensaid second terminal and said potential node, and configured to activatein response to a non-test signal.
 29. The device in claim 28 , furthercomprising a logic unit having said first test signal as a first input,said second test signal as a second input, and having a non-test signaloutput coupled to said third selection device.
 30. The device in claim29 , where said device is configured to avoid simultaneous activation ofsaid first selection device and said second selection device.
 31. Thedevice in claim 30 , wherein: said first terminal is coupled to saidp-channel transistor; said second terminal is coupled to said n-channeltransistor; said potential node of said non-test path is configured tocouple to ground; and said logic unit is a NOR gate.
 32. The device inclaim 30 , wherein: said first terminal is coupled to said n-channeltransistor; said second terminal is coupled to said p-channeltransistor; said potential node of said non-test path is configured tocouple to a non-test voltage source; and said logic unit is a NAND gate.33. A driver circuit for a voltage-pulling device comprising: a firstplurality of potential nodes; a signaling circuit configured to coupleto said voltage-pulling device and selectively communicative with one ofsaid first plurality of potential nodes; and a second plurality ofpotential nodes selectively communicative with said signaling circuit.34. The driver circuit in claim 33 , wherein: said signaling circuitcomprises an inverter having a p-channel transistor coupled to ann-channel transistor; said p-channel transistor is selectively coupledto said first plurality of potential nodes; and said second plurality ofpotential nodes is selectively coupled to said n-channel transistor. 35.A test circuit for a sense amp, comprising: a driver circuit; and acoupler circuit connected to said driver circuit and configured toselectively receive a first voltage source and a second voltage source,wherein said first voltage source is electrically discrete from saidsecond voltage source.
 36. A method for testing a semiconductor memorydevice having at least one sense amp, comprising: writing original datato said memory device; driving said sense amp with a first voltage;reading a first sample of stored data from said memory device; drivingsaid sense amp with a different voltage; reading an additional sample ofstored data from said memory device; and comparing said first sample ofstored data and said additional sample of stored data with said originaldata.
 37. A method for determining the range of margins that avoltage-pulling sense amp transistor of a memory array is capable ofaccommodating, comprising: entering an input test pattern into saidmemory array; reading at least two output test patterns using at leasttwo voltage levels driving said voltage-pulling sense amp transistor;and comparing said input test pattern with said output test patterns.38. A method for determining a lowest reliable level of a supply voltagecapable of driving a sense amp in a memory array, comprising: writinginitial test data to said memory array; initiating a test mode; taking aplurality of test readings from said memory array; decreasing saidsupply voltage driving said sense amp for each of said plurality of testreadings; and repeating taking test readings and decreasing said supplyvoltage.
 39. The method in claim 38 , wherein said repeating furthercomprises repeating taking test readings and decreasing said supplyvoltage until current saturation occurs.
 40. The method in claim 39 ,wherein initiating a test mode comprises providing electricalcommunication between a test pathway and said sense amp.
 41. The methodin claim 40 , wherein initiating a test mode further comprisespreventing electrical communication between a non-test operation pathwayand said sense amp.
 42. The method in claim 41 , wherein decreasing saidsupply voltage comprises decreasing said supply voltage through a rangeof voltages.
 43. A method for determining a highest reliable level of asupply voltage that can drive a sense amp in a memory array, comprising:writing initial test data to said memory array; taking a plurality oftest readings from said memory array; increasing said supply voltagedriving said sense amp for each of said plurality of test readings; andrepeating taking test readings and increasing said supply voltage untilcapacitive coupling occurs.
 44. The method in claim 43 , whereinincreasing said supply voltage comprises increasing said supply voltagethrough a series of discrete values.
 45. A method of test driving asense amp voltage puller for at least one memory cell, comprising:entering an input value to said memory cell; providing a plurality ofdriving pathways to said sense amp voltage puller; configuring eachdriving pathway of said plurality of driving pathways to accept at leasta respective plurality of voltage sources; associating said plurality ofdriving pathways with a plurality of test vectors; transmitting a testvector corresponding to one driving pathway of said plurality of drivingpathways; enabling electrical communication between said sense ampvoltage puller and said driving pathway corresponding to said testvector; reading a first sample of output data; transmitting a differenttest vector corresponding to a different driving pathway; enablingelectrical communication between said sense amp voltage puller and saiddifferent driving pathway; and reading a second sample of output data.46. The method in claim 45 , wherein enabling electrical communicationcomprises enabling electrical communication through one of said drivingpathways at a time.
 47. A method of determining the margin that avoltage-pulling transistor of a memory array is capable ofaccommodating, comprising: entering an input data pattern to said memoryarray; repeatedly reading an output data pattern from said memory array;changing a voltage level driving said voltage-pulling transistor foreach reading; and tracking any differences between said output datapattern and said input data pattern.
 48. A method for determiningoperable drive levels for a pulldown sense amp accommodating anoperations circuit, wherein said pulldown sense amp has a first portionat a first voltage level and a second portion at a second voltage level,comprising: setting an initial drive level for said pulldown sense amp;pulling down said first voltage level for a first time; establishing anew drive level for said pulldown sense amp; pulling down said firstvoltage level for a second time; and selectively comparing one time spanrequired to pull down said first voltage level with a time span foraccessing one of said first and second portions by said operationscircuit.
 49. The method in claim 48 , further comprising equilibratingsaid first voltage level and said second voltage level before eachpulling.
 50. A method for determining the capabilities of a pulluptransistor serving external circuitry, wherein said pullup transistor iscoupled to at least one sense amp, comprising: initiating a test drivevoltage for said pullup transistor; pulling up a digit-line voltage of acomponent of said sense amp associated with said pullup transistor;comparing a length of time needed to pull up said digit-line voltagewith a length of time required to drive said external circuitry;altering said test drive voltage; and repeating said pulling andcomparing.
 51. The method in claim 50 , further comprising altering saidtest drive voltage before every repetition of said pulling.
 52. Themethod in claim 51 further comprising establishing a non-test drivevoltage within a range capable of pulling up said digit-line voltagewithin said length of time required to drive said external circuitry.53. The method in claim 52 , wherein said non-test drive voltage isgenerally constant.
 54. A method of changing the capability of a senseamp driver during a test mode, comprising: providing a first potentialnode for said sense amp driver, wherein said first potential node is ata first voltage; providing a second potential node for said sense ampdriver, wherein said second potential node is at a second voltage; andchanging said first voltage of said first potential node.
 55. The methodin claim 54 , further comprising changing said second voltage of saidsecond potential node.
 56. A method of regulating a control devicewithin a semiconductor device, comprising: driving said control devicewith a first voltage; performing a first operation on said semiconductordevice; driving said control device with a second voltage; andperforming a second operation on said semiconductor device.
 57. A methodof testing a memory device, comprising: performing a plurality ofreadings on said memory device; and initiating a voltage change withinsaid memory device between each reading of said plurality of readings.58. A voltage regulator for a semiconductor device, comprising: aterminal configured to receive a first voltage potential and a secondvoltage potential; an access transistor coupled to said terminal andconfigured to activate in response to receiving a test mode signal; anda connection node coupled to said access transistor and configured tocouple to said semiconductor device.
 59. The voltage regulator in claim58 , wherein: said semiconductor device is configured to operate basedon a source voltage V_(CC) signal; said access transistor has a gate;said test mode signal has a potential generally equal to said V_(CC)signal having undergone a charge pumping process, and wherein said testmode signal is configured to drive said gate of said access transistor;and said voltage regulator further comprises a bootstrap device coupledto said gate of said access transistor and to said connection node,wherein said bootstrap device is configured to prevent said gate of saidaccess transistor from substantially discharging during a transmissionof said test mode signal.
 60. The voltage regulator in claim 59 ,wherein: said semiconductor device includes a cell plate; and saidaccess transistor is configured to couple to said cell plate.
 61. Thevoltage regulator in claim 60 , wherein: said semiconductor deviceincludes a digit line; and said access transistor is configured tocouple to said digit line.
 62. A voltage variance test circuit for asemiconductor device having a connection node, comprising: a firstterminal configured to receive a first voltage potential and coupled toa first exclusively operable access device, wherein said firstexclusively operable access device is coupled to said connection node;and a second terminal configured to receive a second voltage potentialand coupled to a second exclusively operable access device, wherein saidsecond exclusively operable access device is coupled to said connectionnode.
 63. The voltage variance test circuit in claim 62 , wherein: saidfirst exclusively operable access device comprises a first transistorconfigured to activate in response to a reception of a first testsignal; said second exclusively operable access device comprises asecond transistor configured to activate in response to a reception of asecond test signal; and at most one of said first test signal and saidsecond test signal are received at any time.
 64. The voltage variancetest circuit in claim 63 , wherein said semiconductor device has avoltage pulling sense amp transistor, and said connection node iscoupled to said voltage pulling sense amp transistor.
 65. A regulatorfor an equilibration circuit, comprising: a first potential nodeconfigured to receive a first voltage source; a second potential nodeconfigured to receive a second voltage source; a common node selectivelycoupled to said first potential node and to said second potential node;and an output node coupled to said common node and configured to coupleto said equilibration circuit.
 66. The regulator in claim 65 , whereinsaid equilibration circuit has a test mode and a non-test mode, andwherein: said common node is coupled to said first potential node duringsaid non-test mode; and said common node is selectively coupled to saidfirst potential node and to said second potential node during said testmode.
 67. A test driver for a bleeder device joining a cell plate signalgenerator to a memory array, comprising: a plurality of conductive pathsconfigured to receive a plurality of voltage sources; a plurality ofcommunication devices respectively coupled to said plurality ofconductive paths, wherein each communication device of said plurality ofcommunication devices is configured to activate to the exclusion of allother communication devices of said plurality of communication devices;and an output terminal coupled to said plurality of communicationdevices and configured to couple to said bleeder device.
 68. A chargerate regulator for a cell plate generator coupled to a digit line pairof a memory array, comprising: a main transmission device electricallyinterposed between said cell plate generator and said digit line pair;and a drive device coupled to said main transmission device andconfigured to selectively receive a plurality of voltage sources. 69.The charge rate regulator in claim 68 , wherein said drive devicefurther comprises: a plurality of secondary transmission devices,wherein each secondary transmission device of said plurality ofsecondary transmission devices has a first end and a second end,wherein: said first end of each secondary transmission device is coupledto said main transmission device, and said second end of each secondarytransmission device is configured to receive a respective voltage sourcefrom said plurality of voltage sources; and a selective communicationcircuit coupled to said plurality of secondary transmission devices andelectrically interposed between said plurality of secondary transmissiondevices and said plurality of voltage sources.
 70. The charge rateregulator in claim 69 , wherein said selective communication circuit isconfigured to activate one secondary transmission device of saidplurality of secondary transmission devices at a time.
 71. A test modedriver circuit for a regulator device of a cell plate signal,comprising: a conductive path coupled to said regulator device; and avoltage range receiver coupled to said conductive path.
 72. The testmode driver circuit in claim 71 , wherein said voltage range receiver isa contact pad.
 73. A voltage regulator for a memory circuit including anequilibration device, a digit line pair, and a memory cell, comprising:a voltage reception device, wherein: said voltage reception device isconfigured to couple to said memory circuit; and said voltage receptiondevice is selectively electrically communicative with a first testvoltage path and a second test voltage path.
 74. The voltage regulatorin claim 73 , wherein said voltage reception device is configured toelectrically interpose between said equilibration device and said digitline pair.
 75. A defect testing device for a memory array having a cellplate signal device, comprising: a first terminal configured to coupleto said cell plate signal device and configured to receive a voltagepotential; and a second terminal configured to couple to said cell platesignal device and configured to receive a plurality of voltagepotentials.
 76. The device in claim 75 , wherein said second terminal iscoupled to: a first test path configured to receive a first testvoltage; and a second test path configured to receive a second testvoltage.
 77. The device in claim 76 , further comprising: a firstisolation device electrically interposed between said first test pathand said second terminal, wherein said first isolation device has anactive mode and an inactive mode; and a second isolation deviceelectrically interposed between said second test path and said secondterminal, wherein: said second isolation device has an active modecomplementary to said active mode of said first isolation device, andsaid second isolation device has an inactive mode complementary to saidinactive mode of said first isolation device.
 78. The device in claim 77, further comprising a third isolation device electrically interposedbetween said first terminal and said cell plate signal device, whereinall but one of said first, second, and third isolation devices areconfigured to operate simultaneously.
 79. A voltage regulator for a cellplate signal of a memory array, wherein said cell plate signal istransmitted through a conductive path, and a control device is coupledto said conductive path, comprising: a first voltage node having agenerally constant potential; a first latching device coupled to saidfirst voltage node and to said control device; a second voltage nodehaving a variable potential; and a second latching device coupled tosaid second voltage node and configured to couple to said controldevice, wherein said first latching device and said second latchingdevice are selectively operable.
 80. The voltage regulator in claim 79 ,wherein said second voltage node is coupled to a contact pad.
 81. Thevoltage regulator in claim 80 , wherein said first latching devicecomprises a transistor.
 82. The voltage regulator in claim 81 , whereinsaid second latching device comprises: a test signal path coupled tosaid control device; a switching device coupled to said test signal pathand to said second voltage node and configured to allow electricalcommunication between said second voltage node and said test signal pathin response to a reception of a driving signal; a driving device coupledto said switching device and configured to receive a test signal andtransmit said driving signal in response to a reception of said testsignal; and a driving signal maintenance device coupled to saidswitching device and to said test signal path.
 83. The voltage regulatorin claim 82 , wherein said driving device further comprises: a testinitiator configured to receive said test signal and transmit saiddriving signal in response to a reception of said test signal; and anoutput device coupled to said test initiator and said switching device,wherein said output device is configured to receive and output saiddriving signal.
 84. The voltage regulator in claim 83 , wherein: saidmemory array is configured to accommodate an external circuit operatingon a source voltage V_(CC); and said test initiator and said outputdevice are driven by a voltage V_(CCP), wherein said voltage V_(CCP) isgreater than said source voltage V_(CC).
 85. The voltage regulator inclaim 84 , wherein: said control device is a transistor; said switchingdevice is a transistor; said driving signal maintenance device is acapacitor; said test initiator is an inverter; and said output device isa transistor.
 86. An equilibration regulator coupled to a semiconductordevice having a cell plate generator circuit and a digit line pair,comprising: a selective voltage circuit coupled to said cell plategenerator circuit and said digit line pair, wherein said selectivevoltage circuit is configured to receive a plurality of drivingvoltages, and wherein: a selection of at least one driving voltage fromsaid plurality of driving voltages is a test voltage; one of saidplurality of driving voltages is a defect compensation voltage; and saiddefect compensation voltage is a non-test voltage.
 87. The equilibrationregulator of claim 86 , wherein said semiconductor device is generallydriven by a voltage V_(CC), and wherein: said defect compensationvoltage has a potential greater than V_(CC) and is configured tocounteract a defect in said semiconductor device.
 88. The equilibrationregulator of claim 87 , wherein: said digit line pair comprises: a firstdigit line having a voltage potential, a second digit line having acomplementary voltage potential; said digit line pair has a configuredequilibrate voltage generally between said voltage potential and saidcomplementary voltage potential; said defect has a biasing effect onsaid first digit line, wherein said digit line pair approaches a deviantequilibrate voltage in response to said biasing effect of said defect;and said defect compensation voltage has a counter-bias effect on saiddigit line pair, wherein said digit line pair approaches said configuredequilibrate voltage in response to said counter-bias effect.
 89. Theequilibration regulator of claim 88 , wherein: said test voltage has apotential greater than V_(CC) and less than said potential of saiddefect compensation voltage; and said test voltage has an alternatecounter-bias effect on said digit line pair, wherein said alternatecounter-bias effect is less than said counter-bias effect of said defectcompensation voltage.
 90. The equilibration regulator of claim 89 ,wherein said defect compensation voltage is another test voltage. 91.The equilibration regulator of claim 90 , wherein said defect is aconductive path coupling said cell plate generator circuit to said digitline pair.
 92. A method of testing a memory array storing a test datapattern, comprising: allowing a defect to hinder an ability toaccurately read said test data pattern; and preventing said memory arrayfrom restoring said ability to accurately read said test data pattern;reading said test data pattern; and checking said test data pattern forchanges.
 93. The method in claim 92 , wherein preventing furthercomprises preventing said memory array from fully restoring said abilityto accurately read said test data pattern.
 94. The method in claim 93 ,further comprising: changing said test data pattern; writing said testdata pattern to said memory array; and repeating said allowing,preventing, reading, and checking.
 95. A method of detecting any shortfrom a digit line pair to ground, comprising: initiating anequilibration charge of said digit line pair at a charge rate; allowingany short to discharge said digit line pair toward ground at a dischargerate; and decreasing said charge rate.
 96. The method in claim 95further comprising: writing an input data bit to a cell corresponding tosaid digit line pair; reading an output data bit from said cell; andcomparing said input data bit with said output data bit.
 97. The methodin claim 96 , wherein: writing is performed before initiating; andreading is performed after decreasing.
 98. The method in claim 97 ,wherein writing further comprises writing a logic 0 to said cell. 99.The method in claim 98 wherein: initiating further comprises providingelectrical communication between a cell plate generator and said digitline pair; and decreasing further comprises: regulating said electricalcommunication using a control device, and decreasing a driving signal ofsaid control device.
 100. A method of detecting a short from a digitline to a cell plate, comprising: charging said digit line to a firstpotential, wherein said first potential represents a logic value;charging a complementary digit line to a second potential representing acomplementary logic value; allowing said short to urge said digit lineto a third potential; providing electrical communication between saiddigit line and said complementary digit line; allowing said digit lineand said complementary digit line to establish an initial common voltagegenerally between said second potential and said third potential;equilibrating said digit line and said complementary digit line toward afinal common voltage generally between said first potential and saidsecond potential, wherein said equilibrating occurs at an equilibrationrate; and limiting said equilibration rate.
 101. The method in claim 100, wherein charging a digit line further comprises writing said logicvalue to a cell.
 102. The method in claim 101 , further comprisingreceiving a first signal, and wherein allowing said short to urge saiddigit line to a third potential is performed in response to receivingsaid first signal.
 103. The method in claim 102 , further comprisingreceiving a second signal, and wherein providing electricalcommunication is performed in response to receiving said second signal.104. The method in claim 103 , wherein: said first signal has a firstvoltage level; said second signal has a second voltage level; and saidsecond voltage level is higher than said first voltage level.
 105. Themethod in claim 104 , wherein: said first signal has a test duration anda non-test duration; and said test duration is longer than said non-testduration.
 106. The method in claim 105 , wherein said first signal andsaid second signal are RAS signals.
 107. A method of preparing to test astorage capacitor of a memory cell, wherein said memory cell alsoincludes an access transistor and a potential node providing an initialDVC₂ voltage signal to said storage capacitor, and wherein said methodcomprises: turning off said access transistor; providing a forcedvoltage signal to said storage capacitor, wherein said forced voltagesignal has a potential greater than a potential of said initial DVC₂voltage signal; and preventing said forced voltage signal fromsubstantially affecting any digit line associated with said memory cell.108. The method in claim 107 , wherein providing a forced voltage signalfurther comprises providing said forced voltage signal through saidpotential node.
 109. The method in claim 108 , further comprising:providing a main digit line for said memory cell; providing acomplementary digit line for said main digit line; and equilibratingsaid main digit line and said complementary digit line to anequilibration potential generally equal to said potential of saidinitial DVC₂ voltage signal.
 110. The method in claim 109 , wherein saidpreventing further comprises restricting electrical communication ofsaid forced voltage signal to said main digit line and saidcomplementary digit line.
 111. A method of detecting a leak within astorage capacitor of a memory cell affiliated with a digit line, whereina cell plate generator is coupled to said storage capacitor and to saiddigit line, and said cell plate generator is further configured togenerate a voltage, comprising: charging said storage capacitor with aninput potential corresponding to a logic 0 value; initiating a staticrefresh pause; increasing said voltage generated by said cell plategenerator; limiting electrical communication between said cell plategenerator and said digit line; discharging an output potential of saidstorage capacitor to said digit line; and comparing said input potentialwith said output potential.
 112. The method in claim 111 , whereininitiating a static refresh pause further comprises preventingelectrical communication between said digit line and said storagecapacitor.
 113. The method in claim 112 , wherein initiating a staticrefresh pause further comprises allowing electrical communicationbetween said digit line and said cell plate generator.
 114. The methodin claim 113 , further comprising allowing said leak to change saidinput potential to said output potential, wherein said allowing occursduring said static refresh pause.
 115. The method in claim 114 , furthercomprising ending said static refresh pause before discharging.
 116. Amethod of altering a margin between a potential of a charge stored in amemory cell and a common potential of a digit line pair, wherein saidmemory cell and said digit line pair are configured to receive anequilibrate signal, comprising: allowing a defect to change said commonpotential of said digit line pair; and substantially isolating saiddigit line pair from said equilibrate signal.
 117. The method in claim116 , wherein said defect is a short from said digit line pair toground.
 118. A method of altering a margin between a potential of acharge stored in a memory cell and a potential of a shorted digit linepair, wherein said digit line pair is configured to receive anequilibrate signal, and wherein said digit line pair comprises a firstdigit line having a first initial potential and a second digit linehaving a second initial potential, comprising: allowing a defect tochange said first initial potential of said first digit line; shortingsaid first digit line to said second digit line; and substantiallyisolating said digit line pair from said equilibrate signal.
 119. Themethod in claim 118 , wherein: said defect is a short between anequilibrate signal node and said first digit line; and said equilibratesignal node is configured to transmit said equilibrate signal.
 120. Amethod of altering a margin between a potential of a charge stored in amemory cell and a potential of a digit line, wherein said memory celland said digit line are configured to receive an equilibrate signalhaving a voltage, comprising: changing said voltage of said equilibratesignal; allowing said potential of said charge in said memory cell tochange due to a defect and said equilibrate signal; and substantiallyisolating said digit line from said equilibrate signal.
 121. The methodin claim 120 , wherein said defect is a short within a storage capacitorof said memory cell.
 122. The method in claim 121 , wherein said defectis a defect of a dielectric layer between two cell plates of saidstorage capacitor.
 123. The method in claim 122 , wherein said defect isa nitride defect.
 124. A method of generally identifying a defect withina memory circuit, wherein said memory circuit is connected to a cellplate, comprising: writing an input bit to said memory circuit;subjecting said memory circuit to at least one test stage; associatingsaid defect with said test stage; associating an isolation of said cellplate with said test stage; initiating said isolation of said cell platein relation to said test stage; reading an output bit from said memorycircuit; and comparing said input bit with said output bit.
 125. Themethod in claim 124 , wherein: said test stage comprises a prechargecycle; and initiating further comprises initiating said isolation ofsaid cell plate during said precharge cycle.
 126. The method in claim124 , wherein: said test stage comprises a long RAS low period; andinitiating further comprises initiating said isolation of said cellplate after said long RAS low period.
 127. The method in claim 124 ,wherein: said test stage comprises a static refresh pause; andinitiating further comprises initiating said isolation of said cellplate during said static refresh pause.
 128. A method of altering thedrive of a cell plate to digit line bleeder device, comprising: enteringa test mode; providing a plurality of drive voltage sources for saidbleeder device; and applying said plurality of drive voltage sources tosaid bleeder device.
 129. The method in claim 128 , wherein saidproviding further comprises providing a plurality of discrete drivevoltage sources for said bleeder device.
 130. The method in claim 128 ,wherein said providing further comprises providing a range of drivevoltage sources for said bleeder device.
 131. A method of stressing amemory device having a digit line configured to selectively charge to ahigh potential a mid-level potential, and a low potential, comprising:allowing a defect to alter said mid-level potential; and slowing arestoration of said mid-level potential.
 132. A method of testing amemory cell having an equilibrate voltage, a logic voltage correspondingto a logic value, and a margin representing the difference between saidequilibrate voltage and said logic voltage, comprising: enabling anydefect of said memory cell to alter said margin; and reading data fromsaid memory cell.
 133. The method in claim 132 , further comprisingexacerbating any margin alteration from said defect.
 134. A method ofcompensating for a defect within a semiconductor device having a digitline configured to receive a cell plate signal from a signal node,comprising: providing a signal regulator between said signal node andsaid digit line; applying a defect-countering driving voltage to saidsignal regulator.
 135. The method in claim 134 , wherein: said defectcomprises an unregulated electrical communication of said cell platesignal to said digit line; and said defect-countering driving voltage ishigher than a generally standard driving voltage for said signalregulator.
 136. The method in claim 135 , further comprising: testingfor said defect, wherein said testing further comprises: providing saidsignal regulator with a plurality of driving voltages; and selectivelyapplying said plurality of driving voltages.
 137. The method in claim136 , wherein said applying further comprises applying saiddefect-countering driving voltage in response to finding said defect.138. The method in claim 137 , wherein: said method further comprisesinitiating a non-test mode after testing for said defect; and saidapplying further comprises applying said defect-countering drivingvoltage during said non-test mode.